In two former contributions to this Society I described the pharmacological actions of harmaline and harmine, the two alkaloids found in the seeds of Peganum harmala. In regard to harmaline I came to the following conclusions:— “It differs from most alkaloids in that it does not exert, to the same extent as they do, a selective action on one kind of tissue. It attacks not only highly specialised tissues such as voluntary muscle, muscle of the heart, blood-vessels and uterus, and cells of the central nervous system, but also less highly differentiated cells, such as pigment cells, protozoa (Raab), and ciliated epithelium (Jacobson).